Former Wales captain and Sale Sharks Coach Kingsley Jones voiced his concern over Thomas’s selection for the Millennium Stadium showdown following his tough baptism of fire against world champions South Africa in November.
Prop Thomas was a surprise choice at tighthead over Ospreys’ Adam Jones but Williams reckons the three-times capped Newport Gwent Dragons star will silence his critics when he packs down against the formidable Italian forwards.
Williams, 32, said: “Our boys are more than capable of stepping up to the mark. I’ve played against Rhys and know what a handful he is.
“The Italian tight five is their strength and they pride themselves on their scrum. They are renowned for having an awesome pack and we’ve spent a lot of time over the last week on our basics.
“But Rhys will have two experienced players in the front row with him in Gethin Jenkins and Matthew Rees so there are no qualms about him or our front row.”
Thomas is one of six changes made by Wales Coach Warren Gatland as the Three Feathers look to emulate the Grand Slam triumph of 2005 after successive wins over England and Scotland.
Veteran flanker Williams, nicknamed ‘Nugget’, played a starring role in the Slam and has been instrumental this season since being coaxed out of retirement by Kiwi Gatland on the eve of the tournament.
And Williams insists the preparation for the Cardiff clash has been fierce. Williams, capped 78 times by Wales, said: “The intensity of our training is unbelievable and you can’t cruise through a session.
“In the past you may have been able to get away with it but now you feel like you’ve played in a game. There’s no holding back.”